Conservationists have confirmed that at least 26 elephants have been killed by poachers at the world-famous Dzanga Bai, a wildlife viewing site in the Dzanga-Ndoki national park in the Central African Republic (CAR). Four were calves.

The CAR has been unstable since a coup mounted by the Séléka rebel coalition brought down the government of Francois Bozizé on 24 March. Seventeen Arabic-speaking poachers, thought by local ecoguards to be Sudanese, arrived at the park on Monday in a vehicle emblazoned with the Séléka name. They were later seen shooting from a tourist viewing platform overlooking Dzanga Bai.

Dzanga Bai, also known as the "village of elephants", is a large clearing in the rainforest where between 50 and 150 elephants gather every day to drink at mineral-rich springs. This allows visitors and researchers to observe the normally secretive African forest elephant, a different species to the larger savannah elephants found in open country elsewhere on the continent. Two-thirds of the forest elephants have been killed in the last decade.

Bas Huijbregts, head of policy at the World Wildlife Fund's illegal trade campaign in central Africa, said that he could not confirm whether the poachers were in fact under the control of the Séléka group. He said that many armed groups with unclear allegiances had been active in the area, and the WWF's offices in Dzanga-Ndoki had been looted three times since the coup.

Horse-mounted Sudanese ivory poachers have been making dry-season forays into northern areas of the Central African Republic, southern Chad and northeastern Cameroon to hunt savannah elephants for years. They killed over 300 elephants in Bouba N'Djida national park in Cameroon in December.

Sudanese poachers are highly competent hunters – "the very best" – able to kill many elephants at once, said Huijbregts. Dozens of hunters on horseback will corral elephant herds, which are then shot from the saddle. Their ivory is taken back to Khartoum, often via camel, where it is sold into poorly understood criminal smuggling networks.

Although Dzanga-Ndoki national park has armed ecoguards, they felt outgunned by the poachers and did not take them on. "You can't bring a knife to a gunfight," said Rodney Cassidy, the South African owner of an ecolodge in the area. Cassidy and his family fled Dzanga-Ndoki shortly after the coup.

Huijbregts said he was worried that the Sudanese had now turned their attention to forest elephant, adding that its ivory was more desired by Asian ivory carvers, having a distinctive grain and pale pink hue.

Although the poachers have now left Dzanga Bai, the WWF fears the killing may resume. "The Central African Republic must act immediately to secure this unique World Heritage site," said James Leape, WWF International's director general.